This invention relates generally to magnetic recording media, such as magnetic thin film recording disks, and more particularly the invention relates to improving magnetic and parametric performance of such media by the addition of aluminum to a chromium alloy underlayer.
The magnetic disk drive as used for data storage in computer systems comprises one or more disks having thin film magnetic layers on opposing surfaces for the recording of magnetic data as bits along concentric tracks. Typically, as shown in FIGS. 1a, 1b, the disk comprises a substrate 4 of nickel phosphorous (NiP) or ceramic glass on which a plurality of layers are formed by sputtering in a low pressure inert gas atmosphere. The layers include an optional magnetic seed layer 6, a single non-magnetic underlayer 8 (FIG. 1a), or two non-magnetic layers 8, 9 (FIG. 1b), made of either pure chromium (Cr) or a chrome alloy (CrX, CrXY), covered by magnetic layer 10 of a cobalt (Co)-based alloy. A protective layer 12 of sputtered carbon is typically used on top of the magnetic layer and an organic lubricant 14 may be used on top of protective layer.
The chromium underlayer can be a single layer or a multilayer for increased performance. The chromium or chrome alloy has a body centered cubic (bcc, A2) lattice structure which has strong influences on the magnetic properties and the recording performance of the cobalt film. The chrome alloy expands the unit cell so as to improve lattice matching between the underlayer and the cobalt magnetic film. The addition of alloying elements also controls physical properties such as grain size and crystallographic texture, which can play an important role in the performance of the media.
The present invention improves magnetic and parametric performance of a magnetic recording media by adding a small amount (0.5% to 4.0% by atomic weight) of aluminum to a chromium alloy in a single underlayer or multiple underlayer structure.
The added aluminum as a third element in a CrMo alloy underlayer improves recording performance, and when used in a multilayer construction with chromium, the CrMoAl layer increases signal to noise ratio (SMNR). Similarly, the addition of aluminum in CrV alloy enhances signal to noise ratio and reduces intrinsic noise.
The invention and objects and features thereof will be more readily apparent from the following detailed description and dependent claims when taken with the drawing.